1. Field of the Invention
The present invention relates generally to a novel method of producing a color proof of an image to be ultimately printed on a support surface. More particularly, it relates to a method of producing a tone-accurate color proof, process proof or color transfer of an image including a developing step comprising the removal of unexposed ink material by means of a water spray.
2. Brief Description of the Background Art
Presently, color proofs are produced on the surfaces of items such as paper, silicates, metals, acrylic polymers and other substrate materials by complicated procedures. These prior art procedures typically utilize hazardous chemicals for several steps and often require difficult-to-learn or impossible-to-teach techniques. These techniques are generally such that require "the proper touch" or "experience" to achieve a level of perfection or even moderate success. This is in part due typically to the poor adhesion of the color proofing composition to the support sheet.
In a typical color proof production procedure, the support sheet is homogeneously coated with a proofing composition. In practice this composition may be either a solution or a mixture. The composition may contain casein, a primary color pigment and a light sensitive agent. When casein compositions are used, only one certain substrate can be used. The light sensitive agent used, typically a dichromate, is a chemical which drastically changes its solubility upon exposure to actinic light. The composition is dried, usually by evaporating its carrier. Selective transmission of the actinic light is provided by placing an image-bearing negative over the support sheet. The appropriate actinic light source is then energized for a time sufficient to convert and harden the dichromate only in the areas exposed to the light source.
The support sheet is then wetted with the aforementioned composition carrier, with which the converted dichromate previously exposed to the actinic light source is now substantially insoluble. The support sheet is scrubbed and the unexposed composition, which retains its initial solubility with the carrier, is removed thereby. The result of this step is the production of a one color proof of the image on the negative. As most end-uses require four color process proofs, this process is simply repeated three more times, each repetition utilizing different appropriately colored pigments.
Color proofs produced in this manner are extremely useful for final evaluation of print formats before a production run. Properly done, they give precise indication of color break-up and registration. These proofs should contain no optical aberrations. However, a significant drawback is present in existing water developed systems in that the color fidelity of the finished and intermediate proofs is not always desireable, and further, not of a standard considered even minimally reliable. Further, as these proofs are delicate and easily abraded, they require care not commonly found in a business environment. It is obvious that a heretofore unavailable chromatically correct water developed color proof would be a great asset to the printing and graphic industries. Similary, it would be useful to develop a more sturdy or durable proof that is not so often damaged, is less expensive to produce and easy to use.